Designs for enhanced reliability and calibration of landfill gas measurement and control devices

ABSTRACT

An apparatus for sampling landfill gas from a landfill flowing through a pipe. The apparatus may comprise: an enclosure configured to receive a section of the pipe; a gas sampling port in the section of the pipe; at least one sensor device disposed in a region of the enclosure, the at least one sensor being coupled to the section of the pipe through the gas sampling port; and thermal insulation positioned to retain heat from the section of the pipe in the region of the enclosure. A method of operating a landfill gas recovery system. The method may comprise: flowing gas from a well riser pipe through a sampling subsystem to a collection system; and heating a portion of the sampling subsystem with the gas flowing from the well riser pipe to the collection system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority under35 U.S.C. § 120 to U.S. patent application Ser. No. 15/478,583, filedApr. 4, 2017, and titled “DESIGNS FOR ENHANCED RELIABILITY ANDCALIBRATION OF LANDFILL GAS MEASUREMENT AND CONTROL DEVICES”, whichclaims the benefit under 35 U.S.C. § 365(c) and § 120 and is acontinuation (CON) of PCT International Application PCT/US2017/020196,filed Mar. 1, 2017, and titled “DESIGNS FOR ENHANCED RELIABILITY ANDCALIBRATION OF LANDFILL GAS MEASUREMENT AND CONTROL DEVICES” whichclaims priority under 35 U.S.C. § 119(e) to U.S. Provisional ApplicationSer. No. 62/301,922, filed on Mar. 1, 2016, and titled “DESIGNS FORENHANCED RELIABILITY OF LANDFILL GAS MEASUREMENT AND CONTROL DEVICES”.Each of the above-identified applications is hereby incorporated byreference in its entirety.

FEDERALLY SPONSORED RESEARCH

This invention was made with government support under SBIR Phase IIAward No. 1632439 awarded by the National Science Foundation. Thegovernment has certain rights in the invention.

BACKGROUND

Landfills typically produce landfill gas (LFG) as a result ofdecomposition processes of organic waste, and methane is often acomponent of LFG. In order to reduce emissions of methane and othercontaminants in LFG, the landfill sites are typically capped with alayer of cover material and gas extraction systems are installed to pullLFG out before it can penetrate the cover layer and escape. At largersites, these gas extraction systems can consist of a plurality ofvertical and horizontal wells drilled or constructed into the landfill,which are connected with piping to one or more vacuum sources. The coverlayer prevents gas from freely escaping, while the vacuum in theextraction wells pulls LFG into the collection system. LFG extractionwells typically have a manual valve that adjusts the localized vacuumpressure in that well, as well as a set of ports for sampling the gascharacteristics with a portable gas analyzer. Landfill gas is most oftendisposed of in a flare, processed for direct use, or used to powerelectricity generation equipment (such as generators or gas turbines).

The horizontal and vertical wells in the collection system typicallyconsist of a length of perforated pipe connected to a length of solidpipe that rises through the surface of the landfill for wellhead access.The perforated pipe may be laid across the landfill during activedumping and subsequently buried (forming “horizontal wells”) underadditional lifts or inserted into a hole drilled through the landfill(traditional “vertical wells”). This pipe then acts as the gasextraction interface between the fill and the collection system.Additional extraction points may also exist, with collection throughleachate cleanouts, sumps, cisterns, temporary cover layers, and otherpoints of fluid connection with the landfill mass.

SUMMARY

Some aspects include an apparatus for sampling landfill gas from alandfill flowing through a pipe, the apparatus comprising: an enclosureconfigured to receive a section of the pipe; a gas sampling port in thesection of the pipe; at least one sensor device disposed in a region ofthe enclosure, the at least one sensor being coupled to the section ofthe pipe through the gas sampling port; and a wireless transmitter. Insome embodiments, the apparatus may include thermal insulationpositioned to retain heat from the section of the pipe in the region ofthe enclosure.

Further aspects include an apparatus for sampling landfill gas from alandfill flowing through a pipe, the apparatus comprising: a samplingsubsystem comprising: a gas inlet port and a gas outlet port; a regionconfigured to receive a section of the pipe, the section of the pipehaving a gas sampling port; a thermoelectric condenser; at least one gassensor coupled to the gas outlet port; and a gas flow passage from thegas inlet port to the gas outlet port, the gas flow passage passingadjacent to and in thermal contact with the thermoelectric condenser.

Additional aspects include an apparatus for sampling landfill gas from alandfill flowing through a pipe, the apparatus comprising: an orificeblock comprising: a gas inlet port and a gas outlet port; a regionconfigured to receive a section of the pipe, the section of the pipehaving a gas sampling port; and a gas flow passage from the gas inletport to the gas outlet port, the gas flow passage comprising at leastone fluid knock-out. The apparatus may also include a filter for atleast one of a particulate and/or a corrosive gas.

Additionally, some aspects include a method of operating a landfill gasrecovery system, the method comprising: flowing gas from a well riserpipe through a sampling subsystem to a collection system; and heating aportion of the sampling subsystem with the gas flowing from the wellriser pipe to the collection system.

In some embodiments, specially designed consumable or reusable filterhardware and/or features may be employed to actively or passively treatgas that is drawn in and sampled from the LFG stream or atmosphere port,including adsorbent or absorbent filter media, active condensationelements, particulate filters, or screens or knock-outs.

Some embodiments may employ geometrically advantageous designs to ensurewater does not accumulate within the sampling system, for instance byreducing water traps or assuring gravity assists drainage of liquidswherever possible.

In some embodiments, hardware and methods may be employed to allow foreasy field calibration of sensors.

In some embodiments, specially designed features in the orifice plate,the slot into which the orifice plate is inserted, and the lid thatseals the orifice plate into the pipe carrying the gas stream may beemployed to mitigate manufacturing variations and concerns whenmeasuring flow.

Some embodiments may measure the pressure at specific locations in theLFG stream to address limitations in sensing hardware and improve systemtelemetry and control.

In some embodiments, a combination of active and/or passive measures maybe employed to maintain an internal temperature within operating limits.

Some embodiments may employ a front panel used for service tasks such asaccessing consumable or replaceable filter elements, connecting anexternal gas source for calibration, interacting with a user interfaceto control measurement, calibration, and control commands.

Some embodiments may be designed to have specific mechanical featuresand/or be designed for a specific mounting strategy to address thevariety of well styles across different landfills.

Some or all of the components of an apparatus comprising sensors may beformed of a polymeric material. These components may include a regionconfigured to receive a section of pipe and one or more gas flowpassages. The polymeric material may be thermoplastic, thermoset,urethane or a co-polymer, which could be CPVC or HDPE. In someembodiments, an apparatus comprising a sensor may include a port orother connection to a source of gas of known composition, which mayserve as a calibration gas. The apparatus may be controlled to supplycalibration gas to a sensor chamber for making measurements that may beused to calibrate the measurement hardware. One source of a gas of knowncomposition is a source of air, such as the ambient environment. In someembodiments, the at least one source gas of known composition is asource of a mixture of CO₂ and CH₄. In other embodiments, the at leastone source gas of known composition contains a mixture of two gasses ofknown composition. Alternatively, the least one source of a gas of knowncomposition may be a source of air and a source of a mixture of twogasses of known composition. Such a mixture of two gasses of knowncomposition may comprise at least of CO₂ and CH₄.

Some embodiments may be designed to have specific features that allowfor easier handling, installation, and removal of units at a specificsite.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sketch illustrating a landfill gas extraction system,according to some embodiments.

FIG. 2 is a diagram illustrating an exemplary sampling unit, accordingto some embodiments.

FIG. 3 is a block diagram illustrating an exemplary enclosure accordingto some embodiments.

FIGS. 4-6 are sketches illustrating different fluid knock-outs,according to some embodiments.

FIG. 7 is an exploded view of an orifice block and heat managementcomponents, according to some embodiments.

FIG. 8 is a diagram illustrating an orifice block, according to someembodiments.

FIG. 9 is a diagram illustrating an orifice block and a filter,according to some embodiments.

FIG. 10 is a diagram illustrating a manifold, according to someembodiments.

FIG. 11 is a diagram illustrating a calibration port, according to someembodiments.

FIG. 12 is a sketch illustrating installation of an orifice plate,according to some embodiments.

FIG. 13 is a diagram illustrating condensation in a pipe, according tosome embodiments.

FIG. 14 is a diagram illustrating assembling an enclosure with aninternally-routed LFG stream, according to some embodiments.

FIG. 15 is a sketch illustrating a clamshell-style enclosure withinternally-routed LFG stream, according to some embodiments.

FIG. 16 is a sketch illustrating a flange/pipe seal with a pipe,according to some embodiments.

FIG. 17 is a sketch illustrating a component for conducting heat intothe enclosure, according to some embodiments.

FIG. 18 is a collection of sketches illustrating multiple features thatmay be added to the pipe, according to some embodiments.

FIG. 19 is a flowchart of a method for flowing gas, according to someembodiments.

DETAILED DESCRIPTION

The inventors have recognized and appreciated that equipment and methodsfor improving the reliability of sensing the characteristics of the LFGat some or all extraction points improves extraction of LFG. Forexample, insufficient vacuum pressure in a given extraction well canlead to the buildup of gas underground, and may result in fugitiveemissions as excess gas permeates the cover of the landfill and escapesinto the atmosphere. Excessive vacuum can similarly pull atmosphericoxygen into the waste mass, upsetting the anaerobic conditions that arenecessary for methane generation, and if left uncorrected, may lead toelevated subterranean temperatures and a variety of associated problems(including, but not limited to, ground instability, damage to thecollection infrastructure, runaway exothermic reactions, odors, and therelease of toxins and other chemicals that might otherwise remaintrapped underground). As environmental and other conditions in thelandfill change, the rates of gas generation and extraction can becomeunbalanced, requiring an adjustment of the extraction pressure in orderto avoid the problems above. Additionally, tight control of the gascollection system can be used to ensure the optimal or maximum energyproduction when the gas is used as a renewable resource, with thebenefit of minimizing the amount of fugitive gas emissions into theatmosphere. Furthermore, modelling and estimating production (forinstance, for predicting existing capacity in energy markets orpotential capacity for capital investment), or otherwise determining theappropriate set-point of generating capacity or direct use duringoperation, requires sensing of these characteristics of gas generationand extraction.

The inventors have developed landfill gas control and measurement devicethat improves the efficiency of landfill gas extraction. This system,called WellWatcher, includes units that may be installed in-line withthe landfill gas collection system, typically serving as the connectionbetween the wellhead (well riser) and the extraction system (vacuumriser). A system comprised of a plurality of these units is meant toalleviate the need for a constant presence of dedicated personnelattending to each wellhead, so it may be advantageous that the hardwareperform reliably with minimal need for maintenance and technicianattention.

Such units may contain wetted sensors (sensors that require a fluidconnection with the gas stream or a sample of the gas to perform thedesired function—including pressure sensors and gas composition sensorsthat require immersion in the media). The inventors have recognized andappreciated that such sensors are particularly at risk of degrading orfailing to operate properly. They have implemented specificaccommodations in the design and construction of such units to mitigatethe particulate, humidity, and corrosive properties of a landfill gasstream to extend the lifetime and accuracy of any wetted sensors.Furthermore, as this hardware may typically be installed outdoors,certain system design aspects and enclosure considerations may also beimplemented to ensure the internal components remain within acceptableoperating conditions, such as staying above freezing when externaltemperatures are sub-zero in winter months. An additional considerationrecognized and addressed by one or more of the embodiments describedherein, is that this device have access panels, thoughtful mountingfeatures and an adequate strategy for rapid deployment and replacementin the field to minimize effort required during installation and timespent during service, scheduled maintenance, replacement, anduninstallation.

The inventors have recognized and appreciated that a more reliable andcost effective LFG extraction system may be achieved with such animproved sampling unit. A sampling unit may have features that enable itto operate reliably in the harsh environment of a landfill, which caninvolve low temperatures and corrosive gas. To provide such a system,the inventors have recognized and addressed, in one or more of theembodiments described herein, problems, such as:

-   -   LFG exiting a well is typically 99⁺% humidity and may contain        particulate, corrosive or caustic constituents.    -   Condensate or other liquids accumulating or flowing within the        gas extraction system pose an aspiration or ingress risk to        sensing systems that draw a gas sample from this extraction        system.    -   Sensors may need to interact with this gas to measure        characteristics including, but not limited to, pressure, flow,        gas composition, humidity, temperature, etc.    -   Sensors may contain sensitive electronics, optical components,        or otherwise lack protection against LFG constituents, including        liquids such as condensate, or corrosion.    -   Pipes or tubes conveying LFG to the sensing locations (for        example, to a port of a pressure sensor or to a non-dispersive        infrared (NDIR) detector) may become clogged from LFG condensate        or particulates accumulating within these tubes, inhibiting        sensor functionality.    -   Appropriate filters that might mitigate some or all of the        harmful effects of LFG on an LFG measurement system may be bulky        and difficult to integrate inline or in a small form-factor        device, difficult to replace or service, costly to implement,        and often require a specific orientation with respect to gravity        for correct operation.    -   Sensors, in particular gas composition sensors (NDIR,        fluorescence, etc.), often require calibration with one or more        references points. For instance, given controlled test        conditions (such as calibration gasses of known composition), a        two-point calibration might find the difference between expected        reading and actual reading of a sensor at zero and at the rated        range of the sensor to calculate a calibration offset and gain        that are then used to compensate and improve sensor accuracy of        future measurements.    -   Sensor measurements, in particular gas composition sensors        (NDIR, fluorescence, etc.), often exhibit dependence or        sensitivity to factors such as sample gas pressure, temperature,        humidity, and residence time.    -   It is desirable for sensor calibration to occur under the same        conditions—such as pressure, temperature, or sample gas flow—as        would occur during a normal measurement cycle.    -   The measurement and control hardware is typically deployed        outdoors, and may need to survive extreme weather—especially        sub-freezing temperatures.    -   It is desirable for certain sensing elements, such as an orifice        plate used for flow measurement, to be accessible and        interchangeable without disassembling the equipment; flow        measurement range is dictated by the size of the orifice and the        range of the differential pressure sensor that measures the        pressure across this orifice. If the pressure sensor range is        fixed, field adjustment to the flow measurement range when flow        is over or under limits initially assumed—or as flow increases        or decreases over the lifetime of the well—may only be possible        by swapping orifice plates to better match differential pressure        to the measurement range of the pressure sensor. A        field-interchangeable orifice plate, as described herein,        enables such a field adjustment such that the pressure drop        across the orifice plate falls within the range of the pressure        sensor for any installation.    -   It is desirable for certain consumables, such as gas filtration        elements, to be accessible and replaceable without disassembling        the unit—for instance, allowing a technician to replace an        expired, fully consumed, or clogged filter with a fresh one.    -   Health and diagnostics of certain components, such as consumable        filter health, should be measured or inferred and reported so as        to alert technicians of maintenance needs and inform hardware        lifetime planning.    -   It may be desirable for wetted components (those components        interfacing with LFG, sampled or otherwise) to be sealed or        otherwise configured to prevent ingress of LFG into the        enclosure of the measurement and control device, or egress of        LFG into the atmosphere where it can cause an environmental or        safety concern.    -   It may be desirable for components to be manufacturable and        assembled or connected as easily as possible.    -   It may be desirable for field installation, replacement, and        removal of the hardware to be easy, quick, and robust.    -   It may be desirable for installation orientation to be selected        for best performance of internal elements, such as water        knock-outs or sensors, and best control of condensate flow—for        instance, to direct flow through an orifice eccentricity and/or        away from gas sample inlet ports.    -   It may be desirable to reduce the impact of installation to        existing infrastructure—for instance, eliminating any needs to        modify existing wellheads, piping, or other components.    -   Dust, humidity, precipitation, insects, and other detritus are        likely to be present in the environment, so it may be desirable        for equipment design to consider these factors and to mitigate        them.

The inventors recognized and appreciated techniques to address some orall of these concerns and problems associated with measuring theproperties of LFG and controlling the extraction process. The propertiesthat may be measured and/or controlled include, but are not limited to,flow, temperature, pressure, and gas composition. One or more sensorsmay be included to measure one or more of these characteristics of thegas or of the gas flow. Described herein are embodiments for componentsof a system that controls the extraction of LFG at the point ofinstallation of those components, are survivable when deployed in aharsh environment like a landfill wellfield, and/or enable reduction inthe effort and time associated with installing and maintaining fieldunits.

Overview of System Elements

Any suitable combinations of one or more of the following elements maybe implemented in various embodiments of a system as described herein.

LFG Connection—any point in the LFG recovery system that a unit may beconnected to. This could include, but is not limited to, the wellhead,the system vacuum riser, buried or above ground pipes, junctions,flares, blowers, generators or engines, coalescers, filters, pumps,valves, leachate systems, or digesters.

Port—an opening in a connection, pipe, vessel, valve, chamber, or thelike through which air or gas flow or pressure may pass. The port mayhave features such as threading, barbs, or quick-connect geometries orfittings for external connections or jumpers, gaskets, sealing withTeflon tape, or other features. One of the functions of some embodimentsis to make and break connections between two or more ports, with one ormore ports acting as pressure or vacuum sources, flow inlets/intakes oroutlets/exhausts, or sensor interfaces. When a port is referred to inthe context of a valve, the port may either be open (connected to one ormore other ports integral to the valve) or closed (blocked, obstructed).

Pressure—the amount of force exerted over an area, specifically by a gasin some embodiments. Pressure may or may not be associated with acorresponding flow in some embodiments. For example, when measuringstatic pressure, or the pressure (vacuum) within the LFG vacuum systemcompared to atmospheric pressure, with a diaphragm pressure sensor, nosteady-state flow should be passing through the pressure sensor throughits connections to the LFG system. While there may be a transient flowduring the initial connection between two ports such as this, animportant behavior of such a connection that may be found in someembodiments is to convey pressures between ports and not flow of a gas,and it may be specifically referred to as such: a connection ordirection of pressures.

Additionally, other pressure measurements may be used to infer a flow inthe vessel that they are connected to, but again such measurements maybe made with minimal steady-state flow through the correspondingmeasurement ports. This is the case with either differential pressuremeasurements, where pressure is sensed on both sides of a constrictionor orifice 288 in the flow path and where at least two pressures may bedirected to the corresponding pressure sensor ports, or withsingle-ended or impact pressure measurements, such as with a pitot,where a single pressure corresponding to the flow in the vessel may bedirected to the pressure sensor port.

In cases where connections become obstructed (by condensate, particulatematter, etc.), inhibiting a unit's ability to connect either pressure orflow between ports, a transient pressure may be applied by the unit toclear the blockage. The unit may include a controller, which may receiveoutputs of sensors indicating such a condition and, in response,generate control signals for valves or other actuators to apply apressure differential across the blockage. Such a function may beachieved, for example, by connecting one port of the blocked connectionto the LFG vacuum and the other to atmosphere. Such control operationswould, in this case, yield a pressure transient across the ports thatgives way to a steady-state flow once the blockage is cleared.Alternatively, the unit may produce such a pressure by activating a pumpon one side of the blockage. Again, the behavior in this case wouldyield a pressure transient across the ports of the blocked connectionthat gives way to a steady-state flow once the blockage is cleared. Thecleared tube could then be connected as needed to direct pressure orflow unobstructed as desired (and the pump, if used, could bedisengaged).

Pressure may also be described in the context of a steady-state flowwithin some embodiments. Narrow diameters of connections, valves, ports,or other orifices within the unit may create pressure drops during flowof gas. For example, the flow of sample gas into or out of the samplechamber may increase or decrease the pressure within the chamber. Thepressure associated with the flow of gas within the unit may be used toinfer the rate of flow, determine the presence of clogs, or to augmentcertain sensor readings or otherwise provide utility.

Sensor—typically an electronic component that converts a physicalproperty, such as temperature, pressure or gas composition, into anotherform, such as electrical (analog or digital) representation or signal.

Sensor chamber—an enclosed volume within the unit that contains one ormore sensors. A sample gas or purge (clean) gas or air may be passedthrough the chamber through one or more ports, either in a metered(fixed volume) or continuous flow. The sensors within this chamber maymeasure one or more characteristics of the gas passed through thechamber (temperature, humidity, pressure, composition, etc.).Additionally, the sensors may be integrated into the sensor chamberconstruction (for instance, light emitters or detectors, sensor optics,gratings or filters, semiconductors, gas filters, etc.) may beincorporated into a wall, face, boss, lid, or other feature of thechamber. Sensors may also be housed or seated on a circuit board that iseither placed within the chamber or that acts as a face or lid of thesensor chamber. The sensor chamber may have a lid that is removable forservice, sensor replacement, or other actions requiring entry into thechamber. An example is shown in FIG. 10 .

Valve—a mechanical or electromechanical device capable of opening orclosing, either completely or partially, a connection between two ormore ports. In some embodiments, valves described herein may becontrolled by signals output by a controller within or coupled to theunit, allowing automated performance of functions described herein basedon programming or other configuration of the controller.

Solenoid valve—an electromechanical device capable of opening or closinga connection between two or more ports when triggered by an electronicsignal. The solenoid valve may be referred to simply as a solenoid. Thisvalve may also be used to redirect flow or pressure by simultaneouslyopening the connection between one port and another port, while closingthe connection between the first port and a third. The solenoid may alsohave additional states or positions (configuration of port to portconnections), where several ports can be open or connected to eachother, or some or all ports can be closed. The states may be momentary,requiring the electronic signal to be maintained for the duration of thestate, or latched, maintaining state after an electronic signal.

Upstream Pipe—a component that feeds gas from the wellhead to a unit. Insome embodiments, the upstream pipe may pass through the enclosure ofthe unit and may be connected to one end of an electromechanical controlvalve in any suitable way. According to some embodiments, the pipe maybe solvent welded to a union that mates with the electromechanicalcontrol valve. In some embodiments, this union may be drilled and tapped¼-NPT for a stainless steel thermistor. This thermistor may measure thetemperature of the landfill gas and may be constantly immersed in theflow. Additionally, this pipe may have a slot for a configurable acrylicorifice plate, as well as a port drilled on each side of the slot formeasuring pressure and drawing gas composition samples, according tosome embodiments.

Orifice Block/Curved Bolted Block—a member that may serve as amechanical support for some or all of the components described herein.In accordance with some embodiments, the orifice block may be of unitaryconstruction, but in other embodiments, one or more components may beattached to form an orifice block. The orifice block may have integrallyformed therewith, or may have coupled to it, one or more elements thatenable functions described herein. In some embodiments, the orificeblock may mate with the upstream pipe using dynamic seals (O-rings,gaskets) with compression applied using, in some embodiments, a U-bolt,or static seals using solvent or thermal welds or epoxies. According tosome embodiments, the front face (opposite from the pipe) may feature anorifice lid that can be opened, allowing a technician to change theorifice plate. Additionally, this face may contain three quick connectports. The two quick connect ports at the left of the orifice lid mayallow for a technician to install and remove a disposable filter. Thesingle quick connect to the right may be a provision for a gascalibration port.

In some embodiments, the orifice block may include a manifold,comprising one or more passageways through which gas may flow. Inputsand outputs of these passages may be connected to components of thesampling subsystem containing the manifold. The manifold may includecontrollable valves such that gas may flow from selected one or ones ofthe inputs to selected one or ones of the outputs to configure thesampling subsystem for any of a number of operations, includingsampling, calibration, purging, etc. When the manifold is configured forgas sampling, gas may be drawn in through the upstream port (the wellside of the orifice plate), through an integrated water knock-out,across a thermoelectric-chilled cold plate condenser maze on the top ofthe block, back into the block to the bottom left quick connect port,out through the port into an external H2S adsorbent media filter and aparticulate filter, back into the top left quick connect port, and intothe manifold, according to some embodiments. Additionally, the exhaustof this sample gas may return from the manifold back into the orificeblock and out the downstream port (on the valve/union/thermistor side ofthe orifice plate). When the manifold is configured for pressuresensing, no flow may occur; instead, differential pressure may bemeasured through the fluid connection of a differential pressuretransducer to the upstream and downstream ports, while a static pressuremeasurement may be made from a separate transducer teed off of theupstream differential transducer connection, according to someembodiments.

Portions of the apparatus, such as the orifice block and gas flowpassages, may be formed of a polymeric material. Portions formed of thepolymeric material may include the entire enclosure, a region configuredto receive the section of pipe or some or all of the gas flow passages.The polymeric material may be thermoplastic, thermoset, urethane or aco-polymer. In some embodiments, the polymeric material may be CPVC orHDPE.

Manifold and Solenoid Valves—allows multiple valves, four in someembodiments, to reconfigure the fluid connections so both pressuremeasurements and gas samples, as well as purge cycles meant to ejectcondensate from the upstream and downstream ports on the orifice block.The valves, in combination with one or more pumps, may be controlled toimplement a measurement cycle to control sensing of LFG or calibrationgas, purge the system, and/or perform other actions. The manifold mayalso have barbed fittings that are used to convey the differentialpressure and static pressure measurements to pressure transducers in thedevice.

Sample Pump—in some embodiments, differential pressure across theorifice plate may not be enough to fill the sensor chamber during asample cycle, and because gas sensors may not survive direct andcontinuous exposure to the gas stream, a sample pump may be used to drawa timed sample of landfill gas from the pipe, through a filtrationsystem, into the sensor chamber. The manifold then may reconfigure sothis same pump draws in a clean air sample, purging the gas collectionsystem. In some embodiments, the manifold can be reconfigured so thesingle pump can purge both upstream and downstream with clean air, aswell as pump a sample from the upstream to the downstream port via thesensor chamber.

Downstream Pipe—feeds from the electromechanical valve through anenclosure of the unit to the vacuum/extraction system. According to someembodiments, the pipe may be solvent welded to a union that mates withthe electromechanical control valve. Additionally, this union may bedrilled and tapped ¼-NPT for a polypropylene barb that conveys theavailable vacuum pressure to a pressure transducer in the unitmeasurement and control device.

Available Vacuum—typically refers to the vacuum available on the vacuumriser serving a single well or plurality of wells at the extractionpoint, whether naturally occurring or created by a blower or othermachine. The available vacuum may be the vacuum pressure downstream ofthe control valve, and representative of the maximum vacuum that couldbe applied to the extraction point if the valve were fully opened.Available vacuum may be representative of the site-wide system vacuum,but typically less due to pressure drops that occur across the pipesthat convey system vacuum to each extraction point

System Vacuum—typically refers to the site-wide extraction vacuumpressure created by a blower at the flare, generator or otherdestruction device. While a single blower may be used to create theextraction for a given site, some wellfields may employ multiple vacuumsources, such that system vacuum may refer to the individual vacuumsystems or the sum of all vacuums applied to the wellfield.

LFG Stream—feeds from the electromechanical valve through the box to thevacuum/extraction system. According to some embodiments, the pipecarrying the LFG stream may be solvent welded to a union that mates withthe electromechanical control valve. Additionally, this union may bedrilled and tapped ¼-NPT for a polypropylene barb that conveys theavailable vacuum pressure to a pressure transducer in the device.

Applied Vacuum—indicates the amount of vacuum created by avacuum/extraction system.

Fluid—a liquid, vapor, gas, or combination of any or all.

Fluid Connection—any connection between volumes through which a fluidmay flow or pressure may be conveyed.

EXEMPLARY SYSTEM

FIG. 1 illustrates a landfill gas extraction system 100, according tosome embodiments. In some embodiments, a landfill gas extraction system100 may include one or more gas extraction wells 102 coupled to one ormore wellheads 104. In some embodiments, each wellhead may be in fluidcommunication with a single, corresponding well. This well may be one ofany number of wells in a system of wells (not shown). Each well may haveone or more of the following components.

In some embodiments, the landfill gas extraction system 100 of a givenwell may include a gas extraction piping system 108 coupling the well(s)102 to a gas collection system 110, and one or more sampling units 200for sampling the landfill gas. In some embodiments, gas collectionsystem 110 may supply the extracted landfill gas to a gas-to-energypower plant 112, which may convert the landfill gas into electricalpower (e.g., by burning the landfill gas to turn the rotor of agenerator or turbine).

In some embodiments, a control mechanism may operate to improve gasextraction efficiency and/or to control the extraction process for avariety of desired outcomes. Control may be implemented in one or moreprocessors, which may be on one or more printed circuit boards. Thoseprocessors may be implemented in one or more of the units 200. In otherembodiments, the processors may be separate from units 200 containingsensors, but may be in communication, using known wireless or wiredcommunication channels, with the units 200, such that measurements madewith the sensors may be communicated to the processors. Accordingly,each of the units 200 may include a wireless transmitter and/or wirelessreceiver.

The control mechanism may control a control valve, discussed furtherbelow. According to some embodiments, a central controller (not shown)may communicate with the control mechanism and the unit 200 of each wellin a well system. The central controller may transmit commands to andreceive information from the control mechanism of each well.

Examples of control mechanisms and systems according to some embodimentsare described in U.S. Provisional Application Ser. No. 61/899,828,titled “In-Situ Control Mechanisms for Landfill Gas Extraction Wells”and filed on Nov. 4, 2013, U.S. Provisional Application Ser. No.61/913,628, titled “System and Methods for Optimizing Landfill GasExtraction” and filed on Dec. 9, 2013, and U.S. application Ser. No.14/532,807, titled “Devices and Techniques Relating to Landfill GasExtraction” and filed on Nov. 4, 2014, each of which is herebyincorporated by reference herein in its entirety.

FIG. 2 illustrates a sampling unit 200 for sampling landfill gas from alandfill flowing through a pipe 210 according to some embodiments. Insome embodiments, the unit 200 may include an enclosure 220 configuredto receive a section of the pipe 210. According to some embodiments, theenclosure 220 may comprise an hermetic seal, sufficiently blocking theflow of air and/or other gasses and/or fluids that one of skill in theart would consider the enclosure to be air-tight or water-tight.

According to some embodiments, the enclosure 220 may enclose a samplingsubsystem. The sampling subsystem may include a support, such as theorifice block 230 or the enclosure 220 itself. Additionally, thesampling subsystem may include a gas inlet port 236 and a gas outletport 238 mechanically coupled to the support. The sampling subsystem mayalso include a region mechanically coupled to the support and configuredto receive the section of the pipe 210 having the gas sampling port 284.Additionally, the at least one sensor device may be coupled to the gasoutlet port 238.

According to some embodiments, the sampling subsystem may include athermoelectric condenser 234, which is described in more detail below.Additionally, the sampling subsystem may include a gas flow passage fromthe gas inlet port 236 to the gas outlet port 238. The gas flow passagemay pass adjacent to and may be in thermal contact with thethermoelectric condenser 234.

According to some embodiments, the section of the pipe 210 is coupled toa riser pipe of a well 102 in a landfill such that landfill gas from thewell 102 flows through the section of the pipe 210.

According to some embodiments, the unit 200 may also include an orificeblock assembly 230. The orifice block 230 may be disposed in theenclosure 220, as shown in FIG. 2 . Additionally, the orifice block 230may be configured to receive a section of the pipe 210. Orifice block230 may include one or more attachment members that holds pipe 210 in aregion of the orifice block 230. That region of the orifice block mayinclude components that align with openings in the outer wall of pipe210 to enable a sample of gas to be extracted from pipe 210 and/or asample of gas to be returned to pipe 210 after analysis. Unit 210alternatively or additionally may be configured to position sensorsadjacent openings in pipe 210 so as to measure flow of the landfill gasthrough the pipe 210, properties of the gas flow, such as pressure, orcharacteristics of the gas within pipe 210, such as its composition orpercentage or amount of one or more constituent gasses, such as methane,oxygen, carbon dioxide, and/or hydrogen sulfide, for example.

FIG. 3 illustrates an exemplary collection of components that may bewithin enclosure 220, according to some embodiments. In someembodiments, the orifice block 230 may include a gas inlet port 236 anda gas outlet port 238. Additionally, the orifice block 230 may include aregion configured to receive the section of the pipe 210 having a gassampling port.

According to some embodiments, the orifice block 230 may include anattachment member that mechanically couples the orifice block 230 to thesection of the pipe 210 with the gas inlet port 236 of the orifice block230 in gas flow communication with the gas sampling port of the sectionof the pipe 210.

According to some embodiments, the orifice block 230 may include a gasflow passage from the gas inlet port 236 to the gas outlet port 238. Oneor more components may be connected in that gas flow passage tocondition gas before it is exposed to a sensor. Such conditioning mayreduce damage to the sensor from the harmful characteristics of the LFG.For example, the gas flow passage may have at least one fluid knock-out232, which may aid in removing moisture from the LFG. Alternatively oradditionally, the gas flow passage may include one or more filtersand/or may contact components to cool the gas.

According to some embodiments, the unit 200 may include at least onesensor device 240 disposed in a region of the enclosure. The at leastone sensor device 240 may be a gas sensor. Additionally, the unit 200may include thermal insulation 250 positioned to retain heat from thesection of the pipe 210 in the region of the enclosure 220. Suchinsulation may aid in low temperature operation, such as may be expectedin winter conditions. Heat from the gas may be used alone or incombination with other heat sources to ensure that components continueto operate in cold conditions. A sampling unit or an actuator, forexample, might cease to operate or cease to operate accurately ifcondensation formed in the unit and then froze. Other components, suchas a battery, might simply be degraded by cold temperatures, such astemperatures below 32 degrees Fahrenheit, and or all of these componentsmay be heated as described herein.

According to some embodiments, the at least one sensor device 240 may becoupled to the section of the pipe 210 through the gas sampling port.Alternatively or additionally, the at least one sensor device 240 may becoupled to the gas outlet port 238.

As illustrated in FIG. 3 , the unit 200 may include multiple valves orother actuators that may be controlled to allow or clock flow of gasthrough multiple passages. Those passages may, for example, be machinedin a manifold block. Passages, and corresponding actuators, may beincluded in the manifold to implement functions as described herein.Those functions may include passing a gas sample into a sample chamberwhere measurements on the gas composition of gas flow may be made.Additionally, those actuators may be controlled to evacuate the samplegas from the sample chamber and/or inject purge gas into the samplechamber. The gas sample may be landfill gas or may be calibration gas.FIG. 3 illustrates an exemplary configuration that supports thesefunctions. However, other configurations may be used.

Filtration Elements and Methods

To promote the longevity and reliability of sensing devices interfacingwith the LFG stream, some embodiments may employ one or more filtrationelements and methods to reduce the impact of potentially harmfulcharacteristics of the LFG stream. The filtration elements may becoupled in the gas flow passage inside unit 200, or in any othersuitable way. Furthermore, the filtration elements and methods may beimplemented in novel ways to make some embodiments as small, compact,and integrated while still improving filtration efficacy. Certain designconsiderations described herein may reduce the number of tubingconnections, improve reliability of seals, and reduce manufacturingeffort. The following details ways this may be designed and implemented:

Integrated Water Knock-Outs

In some embodiments, the filtration system may contain an integratedknock-out to separate fluids in the gas stream, such as condensate, fromthe gas being sampled. The knock-out (232, for example) may beintegrated into specially designed hardware, such as the orifice block,or a separate unit in line with the sense and measurement system.

According to some embodiments, the at least one fluid knock-out 232 maybe configured to separate at least one fluid from the landfill gas.Additionally, the fluid knock-out 232 may include a vessel having afirst cross-sectional area larger than a second cross-sectional area ofthe gas inlet port 236 and/or a third cross-sectional area of the gasoutlet port 238, as shown in FIGS. 4-7 .

For example, in some embodiments, the knock-out may be implemented byhaving an inlet port or fluid path with a smaller cross-sectional areafeed into a vessel of larger cross-sectional area or volume. Uponaspirating a gas/vapor sample with the undesirable liquid (for example,condensate) present, the liquid will be retained in the bottom of thevessel while the gas/vapor may continue through the outlet path towardsthe top of the vessel.

In some embodiments, this knock-out may be implemented by milling orboring a cavity into a block that serves as a support for other elementsin unit 200 (for example, the orifice block) to connect internal fluidpaths with a smaller cross-sectional area or volume, such that thecavity provides a knock-out volume for aspirated gas/vapor and liquid tobe separated allowing only gas or vapor to proceed to the outlet of thecavity.

In some embodiments, the cross-sectional area or volume of the knock-outmay be selected through calculations or empirical determination ofcharacteristics such as, but not limited to, the velocity of theaspirated fluid, the viscosity of the aspirated fluid, the geometriccharacteristics of the inlet path (such as diameter, cross-sectionalarea or volume), the geometric characteristics of the outlet path, fluidadhesion to the wetted materials, flow duration or total aspiratedvolume in a sample cycle.

According to some embodiments, the at least one fluid knock-out 232comprises a drain port configured to drain the at least one fluid. Insome embodiments, the gas outlet port may include a drain portconfigured to drain the at least one fluid, as shown in FIG. 4 .Alternatively, the drain port may be separate from the gas outlet port238, as shown in FIG. 5 . According to some embodiments, the at leastone fluid knock-out 232 (or the unit 200) may include at least one valveconfigured to open and close the drain port.

For example, in some embodiments, the liquid separated by the knock-outmay drain through the same port through which fluid was drawn, or aseparate port dedicated to draining liquid that may be toggled using adedicated valve.

In some embodiments, this liquid may be actively expelled from theknock-out by reversing flow direction through the vessel—such that thesample inlet becomes the purge outlet—or by the use of a dedicated pumpor valve system designed to extract or expel fluid from the vessel.

In some embodiments, this liquid may be passively expelled through theuse of gravity and the knock-out may employ valves to toggle drainageports.

In some embodiments, the knock-out may employ materials to alter thefluid path (such as porous media, foam, sintered metal, pebbles, orsilica beads) or geometry features such as zig-zags, elbows, or othertortuous paths, to impede the travel of liquids from the inlet to theoutlet.

In some embodiments, the knock-out may be preceded by or include a metalmesh or wool (as shown in FIG. 8 ), such as stainless steel wool, thatprovides both coarse particulate filtration as well as a flame barrier.

FIG. 6 illustrates multiple orientations the at least one fluidknock-out 232 may have. For example, the at least one fluid knock-out232 may be arranged such that a line between the gas inlet port 236 andthe gas outlet port 238 is about 60 degrees from vertical. In someembodiments, the knock-out may be designed to function equally well intwo different orientations that are 90 degrees rotated from each other,such as is shown in FIG. 6 . This design may be useful when the fluidsystem may need to be mounted in a vertical or horizontal position withas little effect on performance as possible.

Active Condensing Element

In some embodiments, an active condensing element may be employed toremove undesirable water vapor from the aspirated gas sample as analternative to or in addition to traditional methods including, but notlimited to, using consumable desiccant media.

In some embodiments, this active condensing element (234, for example)may include a chilled volume through which the aspirated gas is passedto decrease the gas temperature below the dew point, decreasing moisturecontent from the inlet of the element to the outlet as water condensesout along the way.

According to some embodiments, the enclosure 220 may include at leastone active condensing element, such as a thermoelectric condenser 234.The thermoelectric condenser 234 may separate at least one undesiredelement (for example, moisture) from the landfill gas.

According to some embodiments, a gas flow passage of the orifice block230 may pass adjacent to and in thermal contact with the thermoelectriccondenser 234.

According to some embodiments, the thermoelectric condenser 234 mayinclude at least one chilled surface. Alternatively, the thermoelectriccondenser 234 may be covered by at least one chilled plate. In someembodiments, the thermoelectric condenser 234 may comprise at least onechannel at a surface of a block, such as the orifice block 230.Additionally, the at least one channel may direct the landfill gasacross the at least one chilled plate. As shown in FIG. 7 , for example,a thermoelectric element may be mounted on a cold plate that serves as acover on a twisting gas flow passage on an upper surface of the orificeblock 230. The cold plate may retain the gas in the gas flow path, andthe thermoelectric element may be in thermal contact with the gasthrough the cold plate. The knockout 232 may have an opening into thatupper surface such that condensed moisture may be removed through theknockout 232. The twisting gas flow path may increase contact timebetween the gas and the cold plate.

For example, in some embodiments, the chilled volume may be implementedby channels integrally formed with the orifice block 230, such as duringa molding operation.

Alternatively, the active condensing element may include a chilledsurface across which the aspirated gas is passed to decrease the gastemperature below the dew point, decreasing moisture content from theinlet of the element to the outlet as water condenses out along the way.In some embodiments, this chilled surface may be implemented as a faceor faces of a physical block (for example, the orifice block 230) ormanifold that also houses other gas paths or filtration elements.Alternatively, this chilled surface may be attached to a face or facesof a physical block (for example, the orifice block 230) or manifoldcontaining other gas paths or filtration elements.

In some embodiments, this chilled surface may be made from a thermallyconductive metal sheet that may be corrosion resistant (for example, 316stainless steel). In some embodiments, this metal sheet may be chosen tohave specific properties including, but not limited to, good thermalconduction and chemical resistance. Additionally, this metal sheet maybe designed to have a thickness and area, the combination of whichcomprising a characteristic volume, which may be selected throughcalculation or empirical determination to reduce thermal capacitance asmuch as possible and increase thermal conduction as much as possible toimprove efficiency and speed of chilling.

In some embodiments, this metal sheet may be structurally reinforcedwith a more rigid and thermally insulating material that provides a flatcompressing surface and insulation between the chilled surface andambient.

In some embodiments, the face that this chilled surface is affixed tomay contain features (like channels) such as zig-zags, elbows, turns,meanders, or other tortuous routes that direct the gas across thechilled surface in order to optimize the contact time between the gasand the chilled surface.

In some embodiments, the route or routes on this face may be designedusing calculations or empirical determination to maximize chilledsurface area exposed to the gas, minimize the pressure drop from inletto outlet, maximize turbulence or circulation across the chilledsurface, create pressure changes that promote condensation, minimizetraps where condensed liquid might accumulate, ensure manufacturability,and otherwise maximize efficiency of humidity removal.

In some embodiments, the route or routes on this face may be designed topromote purging of condensation from the element when the flow directionis reversed.

In some embodiments, the chilled surface may be cooled through means offorced convection (for example, through the use of a fan), passivethermal conduction or convection (for example, by heat sinking thesurface to a colder environment or ambient temperature), or through a(active) heat pump, such as a solid-state device (for example,thermoelectric) or electromechanical system (for example,compressor-based refrigeration).

In some embodiments, a control system may be employed to selectivelycool the chilled surface at a specific time such as before sampleaspiration to pre-cool the surface or during sample aspiration, andremain off at other times.

In some embodiments, this control system may be open-loop, for instanceoperating for a preset amount of time, at a preset duty cycle or at apreset power level.

In some embodiments, this preset time may be determined throughcalculation or empirical determination to optimize across mostcondensation needs given a range of sample humidity constraints and aspecified power budget.

In some embodiments, this control system may be closed-loop, usingfeedback to regulate a control signal to optimize for goals such asminimal power consumption or maximum filter efficacy. For instance, ifthe ambient temperature and therefore condensing element temperature isalready much colder than the sample gas, the chiller may not need to runas long or as high power to achieve the optimal condensing effect.

In some embodiments, this feedback may be from one or many sensorsincluding, but not limited to, sensors in the LFG path or sample pathmeasuring gas sample humidity, sensors in the LFG path or sample pathmeasuring temperature of the gas, sensors bonded to the heat pump orchilled surface measuring instantaneous output temperature ortemperature sensors measuring ambient or external environmenttemperatures.

In some embodiments, condensate that accumulates in or on the condensingelement may drain passively from gravity or be actively purged byreversing the direction of gas flow through the system.

In some embodiments, the heat pump used to chill the element may also berun in reverse to instead heat the condensing element, assisting in thevaporization and removal of accumulated condensate and drying thecondensing surfaces before the next sample cycle.

In some embodiments, the thermoelectric element may be driven with asingle MOSFET that closes the circuit across a battery and thethermoelectric, or it may be driven by a full bridge (h-bridge) thatallows the reversal of the polarity on the thermoelectric. For instance,the bridge may drive the thermoelectric normally to cool and then inreverse to heat.

Thermoelectric Active Condensing Element Manufacturing Process

In one embodiment, the active condensing element may be constructed fromthe following:

-   -   An indirect gas flow path with inlet and outlet routed on a face        of the orifice block    -   a dovetail or other undercut on this same face meant to hold        captive an O-ring    -   a stamped, cut, waterjet and/or drilled sheet of 316 stainless        steel to serve as the chilled surface    -   a corresponding plate or ‘lid’ of acetal to provide a backing to        the relatively flimsier sheet of 316 stainless steel    -   an O-ring on this same face of the orifice block to provide a        gas-tight seal between the stainless sheet and the tortuous gas        path; this plate contains provisions/cutouts to accommodate for        the thermoelectric volume and the wires that connect to the        thermoelectric    -   threaded inserts on this same face of the orifice block    -   screws (with nylon washers) that drive into the inserts to        compress the acetal against the stainless sheet against the        O-ring to make a gas-tight seal    -   a thermoelectric element, such as a Peltier device, with the        ‘cold side’ (the side of the thermoelectric that chills when        energized with the marked polarity) thermally bonded to the        stainless steel sheet (requiring a cutout in the acetal plate)    -   a heat sink with fan thermally bonded to the ‘hot side’ (the        side of the thermoelectric that heats when energized with the        marked polarity)    -   laser-cut polyamide used to mask thermal compound used in        bonding to the thermoelectric; the polyamide sheet is affixed to        the desired surface (stainless sheet or heatsink) and the mask        is laser-cut in-situ

In this embodiment, the process to assemble the condensing element maybe as follows:

-   -   1. install threaded inserts on face of orifice block    -   2. insert O-ring into corresponding undercut route    -   3. mask the stainless steel cold plate, in this case using a        polyamide adhesive film where the negative was laser-cut        in-situ, by peeling out the negative    -   4. apply thermal compound (epoxy or grease) to plate and        squeegee until it is uniformly covered    -   5. remove the remaining polyamide mask    -   6. place the acetal plate onto the cold plate, aligning        clearance holes    -   7. place the thermoelectric cold-side down on the thermal pasted        section of the cold plate    -   8. place the cold plate onto the corresponding orifice block        face and align the screw clearance holes with the inserts    -   9. apply thread-lock to the screws (with nylon washers)    -   10. mask heatsink using identical method to cold plate and peel        off the negative    -   11. apply thermal compound to heatsink and squeegee until it is        uniformly covered    -   12. remove the remaining polyamide mask    -   13. place heatsink on the exposed thermoelectric face, centering        the thermal paste over the thermoelectric and aligning screw        clearance holes with corresponding inserts    -   14. insert all screws (with nylon washers), compressing thermal        and sealing surfaces and completing assembly

In some embodiments, the mechanism for compressing the sealing andthermal surfaces may be something other than screws, including springs,latches, or clasps.

In some embodiments, compression may be unnecessary after assembly wheninstead replaced with thermal epoxy is used for the thermal connectionsor if a permanent sealant (solvent, RTV, epoxy, etc.) is used for thegas-tight sealing surfaces.

In some embodiments, the gas-tight seal may be made using a flat gasketthat is compressed between the stainless plate and the face of theorifice block.

H2S Adsorbent Media Filter with Particulate and Liquid Barrier

According to some embodiments, the unit 200 may include a filter 260 forat least one of a particulate and/or a corrosive gas. The filter 260 maybe disposed outside the orifice block 230, as shown in FIG. 3 .Alternatively, the filter 260 may be disposed within the orifice block230.

According to some embodiments, the unit 200 may include at least oneconsumable medium 262. In some embodiments, the at least one consumablemedium 262 may be used to scrub at least one contaminant from thelandfill gas. Additionally, the at least one consumable medium 262 mayinclude at least one of an adsorbent activated charcoal, hydrogensulfide, and a disposable cartridge.

For example, in some embodiments, consumable media (for instance, anadsorbent activated charcoal or an iron-based compound) may be used toscrub the hydrogen sulfide or other contaminants (H2S) from the samplegas.

According to some embodiments, the filter 260 may include at least onefine particulate filter located downstream of the at least oneconsumable medium 262. For example, in some embodiments, this media maybe retained using porous foam that also acts as a coarse filter,allowing gas to pass across it but preventing the media fromproliferating beyond the filter ports. In some embodiments, this foammay be chosen to be chemically inert or resistant to H2S.

According to some embodiments, this media may be packaged in a vesselwith an inlet and an outlet port. In some embodiments, this vessel maybe designed for regular disassembly and emptied so that spent media canbe replaced with fresh media (i.e. a “refillable” media cartridge).Additionally, in some embodiments, this vessel may be designed to bedisposable so that an entire spent filter assembly may be economicallyreplaced with a fresh filter.

In some embodiments, this vessel may be designed or chosen to be ascompact as possible. For instance, the vessel may be a length offlexible tubing 280 that can be wound into a compact form factor whilemaintaining a desirable volume and flow path length.

In some embodiments, the length and cross sectional area of the fluidpath may be designed using calculations or empirical determination toapply optimizations including, but not limited to, maximizing gas sampleresidence time on the media and minimizing pressure drop across themedia.

In some embodiments, a fine particulate filter, such as a PTFE membranefilter, may be located downstream of the consumable media to filter dustin the LFG sample as well as dust from the media.

In some embodiments, the particulate filter, such as a PTFE membranefilter, may also serve as a liquid barrier to prevent any liquid thatmanaged to defeat previous mitigation strategies from propagatingfurther through the sampling system

In embodiments, this filter shall be designed for easy service andreplacement. In some embodiments, the system may be designed todetermine when a filter, such as an H₂S scrubber, needs replacement orto project when such a filter will require replacement. Such adetermination or projection may be based on on-going measurements of thefilter's effectiveness.

Effectiveness may be determined, for example, from upstream anddownstream measurements of the component being removed by the filter.For an H₂S scrubber, for example, the effectiveness may be determined bythe ratio of upstream to downstream amount of H₂S measured. In a systemas described herein in which any of multiple locations in the samplingsystem may be coupled to a sensor chamber, such a measurement may bemade by coupling a downstream location to the sample chamber and thencoupling the upstream location. The measured ratio may be compared tothe ratio expected for a properly operating filter. For example, aproperly operating filter may remove at least 50% of the component.

A comparison of upstream to downstream amounts of the component mayalternatively or additionally be based on an amount of the componentremoved by the filter rather than a ratio. For example a properlyoperating filter may remove at least 500 ppm of the gas. Alternativelyor additionally, the amount of the compound removed may be based both onconcentration and flow rate, yielding an amount of the component removedfrom the gas per second, which can be compared to a rated value for aproperly working filter.

These or any other suitable upstream to downstream comparison may becompared to rated values for a properly operating filter. If thecomparison indicates effectiveness below the rated value, a message maybe sent by the system controller, alerting an operator to change thefilter. Alternatively or additionally, the effectiveness may be trackedover time, by the controller of the sampling subsystem or othercomputerized device coupled to the controller. The rate of change ineffectiveness may be used to predict a time when the effectiveness willbe below the rated value for a properly operating filter, allowing anoperator to plan for maintenance.

Manufacturing Process

In one embodiment, the consumable filter may be constructed from thefollowing:

-   -   a longer length (around 18 inches) of plasticized PVC tubing        that provides the gas path through the filter media    -   a quick-disconnect fitting (for easy removal) that mates with        the unfiltered LFG sample port on the orifice block and inserts        into the longer length of tubing    -   adsorbent filter media loaded into this longer length of tubing    -   porous polyamide foam plugs, inserted into this longer length of        tubing after filter media is loaded    -   a PTFE membrane filter with barb fittings on both sides, with        the inlet port inserted into the longer length of tubing    -   a shorter length (about 4 inches) of plasticized PVC tubing that        provides the gas path from the outlet of the PTFE membrane        filter back into the orifice block    -   a quick-disconnect fitting that mates with the filtered LFG        sample inlet port on the orifice block and inserts into the        shorter length of tubing

In this embodiment, the process to assemble the consumable filter:

In some embodiments, the PTFE filter may also include quick-disconnectfitting 282 connections to the tubing, allowing it to be treated as aseparate consumable.

In some embodiments, the consumable filter assembly may instead bedesigned as a disposable cartridge with PTFE membrane, filter media andporous foam entirely integrated.

In some embodiments, this disposable cartridge may be made fromthermoformed plastic, such as PETG, with a bonded film sealing acrossthe top.

In some embodiments, this disposable cartridge may be manufactured insuch a way that the film, otherwise entirely sealing the cartridge, canbe punctured at the inlet and outlet ports through a mating clasp on thedevice assembly.

In some embodiments, this disposable cartridge may be manufactured insuch a way that the puncture location has features designed to create agas-tight seal with the mating clasp on the device assembly.

Orientation and Design of Fluid Paths to Minimize Fluid Accumulation

In some embodiments, the orientation and direction of fluid paths,including but not limited to, routed or drilled channels, tubing used toconvey gas flow or pressure, or pipes and pipe nipples may beconstructed or arranged in such a way that the lowest point in the pathdoes not create a trap, s-bend, or u-bend where liquid can accumulate.

In some embodiments, the orientation and direction of these fluid pathsmay be designed such that the lowest points contain a port, drain, oroutlet through which any accumulated liquids may naturally drain or bepurged.

In some embodiments, the orientation and direction of fluid or pressureports may be designed in such a way to preferentially point towards oraway from, but not normal to, the direction of gravity. As can be seenfor example, in FIGS. 7 and 8 , a unit 200 may contain an orifice block230 that has a region configured to receive a section of pipe 210. Thatregion may fix the orientation of the orifice block 230, and the othercomponents of unit 200, relative to the pipe 210. By configuring theorifice block 230 for attachment to a horizontal or vertical pipe, theorientation of components in unit 200 with respect to gravity may beestablished.

In some embodiments, the location of these ports on any chambers,vessels, or volumes may be preferentially located at the top and/orbottom of the chamber, vessel, or volume with at least one port on thebottom so that any accumulated fluid may purge through the bottom port.

In some embodiments, these chambers, vessels or volumes maypreferentially have inlet and outlet ports on opposite sides to promotecomplete exchange of the fluid in the vessel during purge or samplecycles.

In some embodiments, the fluid paths, chambers, vessels, or volumes mayinclude additional ports or routes located at the lowest point in thepath, chamber, vessel, or volume—especially in cases where it may not bepossible to locate the inlet or outlet ports at the lowest point—tofacilitate draining of accumulated fluids.

In some embodiments, it may be advantageous to orient flow paths at a 45degree angle such that orienting the device horizontally or verticallystill allows for adequate performance.

In some embodiments, fluid handling hardware including, but not limitedto, valves and pumps, may be installed in an orientation to ensure thatthe internal geometry of does create a low point that encourages liquidaccumulation or inhibits liquid evacuation. For instance, a valve may bemounted to a manifold with ports facing downward towards gravity,allowing liquids to naturally drain, as shown in FIG. 10 . Likewise, apump may be installed onto a manifold such that the inlet and outletports face downward, allowing liquids to naturally drain.

In some embodiments, a coalescing element may be added to all gas inletsinto this gas sampling system. In some embodiments, this coalescingelement may be a metal mesh or wool, such as stainless steel wool. Insome embodiments, this coalescing element may also function as a coarseparticulate filter, a flame barrier, or a condensing element if it iscooler than the gas passing through it.

Techniques for Robust Measurements

Calibration Devices and Methods

According to some embodiments, the unit 200 may include at least onecalibration port 239, as shown in FIGS. 3 and 11 . Some embodiments mayemploy a calibration port 239 configured for connection to a source of agas of known composition and for aspirating such a gas of a knowncomposition for sensor calibration. For example, the calibration port239 may be used to aspirate at least one gas of a known composition forcalibration of the at least one sensor device 240. In another example,calibration port 239 may be used to aspirate outside air for calibrationof the at least one sensor device 240. In such an embodiment,calibration may be based on measuring ambient oxygen. As the amount ofambient oxygen is readily constant, calibration with outside air as thecalibration gas can provide a simple mechanism to frequently calibratean oxygen sensor.

Moreover, in some embodiments, sensors that operate on the sameprinciple as an oxygen sensor may be calibrated based on the oxygensensor calibration. For example, oxygen, methane and carbon dioxide mayall be measured with a non-dispersive IR sensor. Sensors for methane andcarbon dioxide may require the same calibration factors as an oxygensensor, which may be determined based on the calibration measurements onthe oxygen sensor. One or more calibration ports may be coupled to oneor more sources of gas of known composition. In some embodiments, thatgas of known composition may be air. In this embodiment, the calibrationport may be exposed to ambient air. In other embodiments, the one ormore sources of gas of known composition may be gas canisters, filledwith calibration gas of known composition or other suitable mechanism toprovide calibration gas. In these embodiments, the at least one sourcegas of known composition may be a mixture of CO₂ and CH₄. In yet otherembodiments, the apparatus may be configured to couple gasses of two or,in some embodiments, more sources of calibration gas. Those sources mayinclude a source of air and a source of gas that is a mixture of atleast CO₂ and CH₄. As a specific example, a calibration gas may comprise35% CO₂, 50% CH₄, and 15% N₂. Here, percentages may be determined in anysuitable way, including by volume, mass, molar fraction or partialpressure. As another specific example of a calibration gas that might beused, the calibration gas may be a calibration gas used in the industryfor calibration of handheld devices, consisting essentially of 35% CO₂,50% methane, and 15% N₂, with minor deviations as a result of impurities

In some embodiments, this calibration port 239 may be installed in thegas sampling path so the calibration gas may pass through the same fluidsystem, including filters, valves, and knock-out vessels, as the gassample from the LFG stream.

In some embodiments, this calibration port 239 may be used inconjunction with a valve 235 that diverts the sample path from the LFGstream to the calibration port. The valve 235 may be connected betweenthe calibration port 239 and a sensor, so as to enable gas to flow fromthe calibration port to the sensor.

In some embodiments, this valve 235 may be integrated into thecalibration port 239 such that insertion of a fitting into thecalibration port 239 toggles the diversion of the sample path from theLFG stream to the calibration gas, and back again upon removal.Additionally, this valve 235 may be toggled through an electronic devicethat may be signaled by a command on a user interface or by thedetection of a fitting connected to the calibration port 239.

In some embodiments, this valve 235 may be toggled through mechanicalaction, such that insertion of a fitting into the calibration port 239mechanically actuates the integrated valve.

In some embodiments, this calibration port 239 may be installed in aseparate location in the gas sampling path, possibly bypassing some orall of the paths used to sample gas from the LFG stream.

Some embodiments may employ a calibration method that requires the useof a comparable gas path in instances where diversion of the gas samplestream may not be applicable or practical. For instance, even thoughcalibration gas is nominally clean, it may still be advantageous to passthe gas through an characteristic device, such as but not limited to anexternal filter, vessel or length of tubing that may emulate the sameeffects such as, but not limited to, mixing volume, fluid path length,chemical reactions or pressure drop as filters or volumes of the normalgas sampling path. This way, effects of the filter and sampling path maybe accounted for in the calibration process.

Some embodiments may employ a calibration process comprising cycles thatsample two or more gas mixtures of known and different composition tocalculate linear (gain and offset) or nonlinear compensation for asingle gas sensor.

Some embodiments may employ a calibration process comprising cycles thatsample two or more gas mixtures of known, different and linearlyindependent composition or pure gasses to calculate linear (gain andoffset) or nonlinear compensation for one or more gas compositionsensors at a time.

In some embodiments, two gas mixtures of known composition may bemeasured to calculate the span or gain factor and zero offsets of one ormore internal gas composition sensors, with the gain and offset appliedto the measured value to yield a corrected value. For example, a gaswith the known concentrations of 50% methane, 35% carbon dioxide and theremaining balance (15%) nitrogen by volume may be used to calculate thespans of a methane and/or carbon dioxide sensor and the zero offset ofan oxygen sensor. Similarly, clean atmospheric air with the relativelyconsistent concentration of approximately 20.9% oxygen and nearly all ofthe remaining concentration as nitrogen may be used to calculate thezero offsets of a methane and/or carbon dioxide sensor and the span ofan oxygen sensor.

In some embodiments, the two or more gas mixtures of known compositionmay have non-zero concentrations for all gases being measured as long asthe different gas mixtures comprise a linear combination ofconcentrations that occupies the basis vectors necessary to calculate acalibration for each sensor.

In some embodiments, it may be necessary or desirable to calibrate thegas sensor for each constituent gas individually with one gas mixture ata time to reduce cross sensitivity from other gasses in the calibrationmixture.

In some embodiments, in an alternate sensor configuration sensors may becalibrated simultaneously to directly calculate and compensate for crosssensitivity across gasses in the measurement. For instance, calibrationmight use a mixture with concentrations of each gas, possibly usingconcentrations typical of those found in an LFG stream.

Some embodiments may employ a calibration process comprising cycles thatsample two or more gas mixtures of known and different composition attwo or more absolute pressures to calculate linear (gain and offset) ornonlinear compensation to correct for effects of pressure on themeasurement.

In some embodiments, the sample pump that draws in the gas sample (andcalibration sample) may be throttled to create these conditions ofdifferent absolute pressure and flow within the gas sample chamber thathouses the gas composition sensors.

In some embodiments, this gas sample chamber pressure may be measured byone or more pressure sensors and may be used in the determination of thepressure compensation factors during a calibration.

In some embodiments, this gas sample chamber pressure reading may beused when applying pressure sensor compensation during normalmeasurement cycles to correct for the effects of pressure on thecomposition sensors.

Some embodiments may measure one or more pressures through the use ofdigital pressure transducers that may or may not have a zero offset.

In some embodiments, the output or value of these digital pressuretransducers may be recorded during a calibration period of zero appliedpressure and applied as an offset during an active measurement toeliminate offsets and improve sensor accuracy.

Measurement Hardware and Methods

In some embodiments, flow may be determined using a differentialpressure device, such as but not limited to, an orifice plate, such asis shown in FIG. 12 .

In some embodiments, the process to manufacture this orifice plate maybe imperfect and cause repeatable manufacturing artifacts, such as ataper on the orifice bore (shown in FIGS. 12 and 13 ). For instance, theuse of a laser cutter to create an orifice plate from acrylic stock maycreate a taper in the orifice bore cut.

In some embodiments, artifacts such as this taper may be mitigated byensuring that the artifact is consistently reproduced across the entirebatch and that the device is used in the same position each time.

In some embodiments, this orifice plate may utilize a polarizing featuresuch that the insertion of the orifice into some embodiments for the usein flow measurement is permitted to occur in only one way. For instance,adding a polarization tab to the orifice plate and the correspondingslot in which it is inserted would add this chirality.

In some embodiments, variations in the orifice plate or the pipe inwhich the orifice plate is inserted may make a perfect seal around theorifice plate and the inner pipe wall difficult to achieve. Forinstance, eccentricity caused in the CPVC pipe production process makesa perfect concentric and co-radial mate impossible.

In some embodiments, the orifice plate may be designed with a slighteccentricity that conforms to or otherwise minimized variation from theeccentricity of a particular batch or manufacturer of CPVC pipe.

In some embodiments, this orifice plate may be compressed against thepipe wall to assist in sealing between the orifice plate and the innerpipe wall (see FIG. 12 , for example). As described herein, an orificeblock 230 may include one or more attachment members. The attachmentmembers, for example, may be U-shaped members that fit around the pipe210. The ends of the members may pass through the orifice block 230 andmay be threaded. By tightening a bolt, or otherwise drawing theattachment members toward the orifice block 230, the pipe may becompressed against the orifice block 230.

In some embodiments, the amount of compression may be calculated orotherwise empirically determined and then applied through the use of aspecific groove, slot, pocket or other feature on a lid covering theslot in which the orifice plate is inserted, examples of which are shownin FIG. 12 .

In some embodiments, this feature may also contain an elastomeric (shownin FIG. 12 ) or otherwise compressible material that can deform whencompressed between the lid and the orifice plate to reduce thecompression stress applied to the orifice plate.

Some embodiments may conduct a static pressure measurement of the LFGgas stream.

In some embodiments, this measurement may be conducted using a digitalunidirectional pressure transducer that accurately measures positivepressures but not negative pressures, or vice versa.

In some embodiments, when installed on a well or extraction point withvery low applied vacuum (such that the well static pressure is nearly atequilibrium with atmospheric pressure) this unidirectional measurementmay be preferentially conducted using the port meant to convey pressuredownstream of the orifice to ensure measurement of static pressureswithin the range of the device; given normal flow from a well throughthe device, the orifice plate will drop an amount of pressure with anyflow through the LFG port ensuring the static pressure measured at thedownstream port, relative to atmosphere, be of constant sign.

Some embodiments may be installed on an LFG stream with a high volume offlowing condensate, such as is shown in FIG. 13 .

Some embodiments may be oriented in such a way that the flow through theorifice plate bore is normal to gravity such that flowing condensate mayperiodically accumulate on the cusp of the top or upstream of theorifice plate, as shown in FIG. 13 .

Some embodiments oriented in this way may be preferentially designed todraw in the LFG gas sample through the downstream, or bottom, port toavoid pulling in liquid that may accumulate on the top, or upstream,side of the orifice plate.

Some embodiments may contain a control valve that regulates theimpedance between a central vacuum system (available vacuum) and the LFGextraction point so as to correspondingly control flow from or appliedvacuum to the extraction point.

Some embodiments may employ a digital pressure transducer to measure thevacuum on the downstream side of the control valve to provide anindication of the maximum system vacuum that could be applied to thatextraction point.

In some embodiments, this available vacuum measurement may be combinedwith a pressure measurement upstream of the control valve to compute adifferential pressure measurement across the valve.

In some embodiments, a differential pressure measurement across thevalve may be combined with other information or measurements including,but not limited to, pressures, temperatures or rate of flow (from a flowmeasurement device in the same gas stream) to generate an impedanceprofile that correlates measured pressures (static and/or differential)and valve position to a corresponding valve impedance.

In some embodiments, this differential pressure measurement across thevalve may be combined with other information or measurements includingbut not limited to, valve position (percentage open or closed), staticpressure or temperature to infer the rate of flow of the LFG gas stream.

In some embodiments, this differential pressure measurement may be usedas a feedback signal in a closed-loop control system that controls thevalve position (percentage open or closed) in order to modulate the flowand extraction pressure.

In some embodiments, this available vacuum measurement may provideindications of system level behavior that may otherwise be difficult todetermine. For instance, a drop in static pressure may be caused by adrop in system vacuum pressure instead of increase in flow or change ingas generation characteristics. Similarly, effects of a valve command onan individual well to the extraction system may be observed on deployedunits with fluid connection to the extraction system without confoundingmeasured pressure dynamics of the individual extraction points.

Some embodiments may employ one or more mitigation strategies to preventcondensate in the gas stream from interfering with the available vacuummeasurement including, but not limited to, a knock-out or water trap,valves or pumps used to actively purge the measurement port, or a PTFEmembrane filter.

In some embodiments, these mitigating features on the available vacuumport may be preceded by or include a metal mesh or wool, such asstainless steel wool, that provides both coarse particulate filtrationas well as a flame barrier, as shown in FIG. 8 .

In some embodiments, this available vacuum knock-out may be passively oractively drained, such as is shown in FIGS. 4, 5, and 8 .

In some embodiments, this knock-out and the entire fluid connection tothe available vacuum transducer may be actively drained or purged bymomentarily opening a connection from atmosphere to system vac throughthe available vacuum connection. For instance, under normal operation anormally closed valve may toggle open to allow a burst of atmosphere tobe drawn through the available vacuum transducer connection by thesystem vacuum, pushing any accumulated condensate back through the portinto the LFG stream.

Some embodiments may employ a port that connects internal fluid systemsto atmosphere.

In some embodiments, this atmosphere port may be fluidly connected to areference port on a pressure transducer to act as a reference formeasurements such as static pressure or available vacuum.

In some embodiments, this atmosphere port may be used as an inlet sothat clean air may be drawn in for use in purging one or more parts ofthe fluid handling system. For instance, a pump may actively pump thisclean air through the sampling system to purge accumulated fluids.Likewise, a normally closed valve may open to allow the system vacuum todraw in clean air to similarly purge accumulated water back into the gasstream.

Some embodiments may employ a sample cycle that entirely purges the gasin the sampling system with clean air after each measurement. Forinstance, exposure of the gas sensor (or other hardware, such as pumps,valves, or filter elements) exposure to the potentially corrosive anddirty LFG sample may be limited by purging the gas sample from thesensor chamber and any fluid paths with clean air from this atmosphereport.

In some embodiments, this atmosphere port may employ one or moremitigation strategies to prevent aspiration of precipitation orcondensation including, but not limited to, a knock-out or water trap,valves or pumps used to actively purge the measurement port, or a PTFEmembrane filter.

In some embodiments, these mitigating features on the atmosphere portmay be preceded by or include a metal mesh or wool, such as stainlesssteel wool, that provides both coarse particulate filtration as well asa flame barrier.

In some embodiments, a coarse mesh, foam, or wool that may or may not bethe same as this coarse particulate filter or flame barrier may beemployed to prevent spider, insects, dust, plants, or miscellaneousdetritus ingress.

Designs for Surviving Sub-Freezing Weather

Some embodiments may employ an insulated and/or air-tight or sealedenclosure (such as enclosure 220 shown in FIGS. 2, 14, and 15 ) toretain heat within the enclosure.

Some embodiments may employ nonmetallic (or otherwise non-thermallyconductive) mounting features, including but not limited to, standoffsor screws, to convey mechanical support through the insulation to theenclosure or structures outside of the enclosure to reduce thermalshorts associated with these voids in the insulation.

Some embodiments may be designed to route the warm LFG gas stream,specifically a pipe (such as pipe 210 shown in FIG. 2 ) carrying thewarm LFG stream, through the enclosure of some embodiments to provide apassive heat source within the enclosure.

In some embodiments, the enclosure may carefully be designed in such away as to accommodate for the pipe carrying the LFG stream in a mannerconducive to improved manufacturability and serviceability. Forinstance, cutouts in a simple box with a lid may be less advantageousthan designing the enclosure to part in the direction axially with thepipe, or part in a clamshell style radially with the pipe, as shown inFIG. 15 .

In some embodiments, the enclosure may be designed with special featuresto independently seal against the enclosure and the pipe to promoteeasier assembly and serviceability. Examples of static and dynamic sealsare illustrated in FIGS. 15 and 16 .

In some embodiments, this pipe may be constructed from a chemicallycompatible metal, such as stainless steel, to enhance thermal conductionfrom the warm LFG gas stream to the inside of the box. Alternatively,this pipe may be constructed from a chemically compatible plastic, suchas CPVC, with lower thermal conductivity than a corresponding metal pipeto reduce cost or weight or improve manufacturability.

According to some embodiments, the unit 200 may include at least onethermal conductivity component configured to enhance a thermalconductivity of the section of the pipe 210. For example, the thermalconductivity component may be a corrosion resistant metal heat sink,such as that shown in FIG. 7 . Alternatively or additionally, the unit200 may include at least one fan configured to circulate air across thesection of the pipe 210. For example, FIG. 7 illustrates a fan with theheat sink, although the fan could be positioned in any suitable way.

For example, in some embodiments, thermally conductive features may beadded to the plastic pipe to enhance thermal conductivity, although somesuch features may be used with other materials of pipe. In someembodiments, a corrosion resistant metal heat sink may be inserted intothe LFG gas stream through a sealed port in the pipe wall, or a segmentof the plastic pipe maybe replaced with a segment of corrosion resistantmetal—both acting to conduct heat from the gas stream across the pipewall into the enclosure. Examples of heat sinks in some embodiments areshown in FIGS. 17 and 18 .

In some embodiments, the LFG gas stream may be directed through acomponent that has the purpose of conducting heat from the LFG gasstream into the enclosure. Additionally, this component may be anorifice plate (such as that shown in FIG. 12 ) that, while normally usedfor flow measurement, is also designed to conduct heat from the LFGstream into the enclosure.

In some embodiments, devices or features may be added to the pipe (metalor plastic) carrying the LFG gas stream to improve convection. Forinstance, heat sink fins, thermally conductive panels, and/or thermallyconductive slices (such as shown in FIG. 18 ) may be added to the pipeproviding increased passive convection from the pipe wall. Similarly, afan may be added to circulate air inside the enclosure across the pipe,providing forced convection from the pipe wall.

According to some embodiments, the unit 200 may include at least oneactive heating element 290 configured to emit heat within the enclosure220. Additionally, the unit 200 may include at least one controller 292configured to control the at least one active heating element.

For example, some embodiments may employ active heating elements withinthe enclosure at the cost of an increased power budget. In someembodiments, a control system may be used to regulate the power, dutycycle or other signal driving the forced convection or heating element.

In some embodiments, this control system may operate as a closed-loopthermostat using a combination of some or all measurements including,but not limited to, the internal box temperature, LFG gas streamtemperature, available battery charge or available power supply voltageas feedback. For instance, the control system may try to maintain aspecific or minimum internal box temperature, but optimize performancebased on the available thermal capacity of the LFG stream or powerbudget.

In some embodiments, a system level controller governing a plurality ofunits may be used independently or in conjunction with the individualtemperature controllers in each unit to optimize power budget forheating use during current or forecasted cold weather. For instance,reducing frequency of measurement cycles or otherwise throttling backauxiliary power consumption could save energy to instead be used forheating.

In some embodiments, a system level controller may be used independentlyor in conjunction with the individual temperature controllers in eachunit to optimize power budget (potentially, but not necessarily, forheating use) during periods of reduced battery charging by reducingfrequency of measurement cycles or otherwise throttling back auxiliarypower consumption. For instance, a cloudy forecast could prompt thecontroller to signal solar-recharged units to reduce power consumptionuntil the dawn of a sunnier day.

In some embodiments, the thermal mitigation strategy may be optimized bycalculating the relative gains and losses in thermal impedance forvarying enclosure insulation thicknesses and material types, active andpassive heating capacities, and the relative tradeoffs againstconstraints such as, but not limited to, size, cost, and weight. Forinstance, calculations and empirical results may indicate that adding anextra inch of insulation may be less effective at keeping someembodiments warm than adding forced air convection to the pipe carryingthe LFG stream.

In some embodiments, the active heating element may be the waste heatfrom another system, such as the hot side of a thermoelectric condenserused in gas sample filtration.

Simplifying Hardware Installation and Maintenance

Site Installation and Mounting Considerations

Some embodiments may be designed to mate with existing infrastructuremost commonly found at a landfill wellfield, such as vacuum hoses,wellheads, or elastomeric reducing couplings.

According to some embodiments, the unit 200 may include at least oneadjustable mounting apparatus configured to mount the enclosure 220 toat least one of an existing well riser pipe and/or an existing well head104.

According to some embodiments, at least one end of the pipe 210 mayinclude a shape configured to couple with an existing well riser pipe,an existing well head 204, an existing vacuum hose, and/or an existingelastomeric reducing coupling. For example, the shape may comprise atleast one taper.

According to some embodiments, mounting features on some embodiments maybe designed in such a way allow for cantilevering off of an existingwellhead or well riser. Alternatively or additionally, mounting featureson some embodiments may be designed in such a way allow for verticalmounting such that the mounting feature runs parallel to the gas flowpath.

In some embodiments, this mounting feature or strut may be banded,clamped, or strapped to the corresponding well or vacuum riser toprovide support when some embodiments—specifically one end of theLFG-carrying pipe running through the unit—are installed directly intothe elastomeric coupling.

In some embodiments, it may be advantageous to use a specially taperedinstallation plug to cap the vacuum coupling during installation,reducing the likelihood of excess atmosphere/oxygen entering theextraction system.

In some embodiments, when one end of the LFG-carrying pipe is installeddirectly into the elastomeric coupling, the other end of theLFG-carrying pipe may be connected directly to the vacuum hose.

In some embodiments, when one end of the LFG-carrying pipe is connecteddirectly to the vacuum hose, clamps, bands or straps may be used totighten around the hose to make a seal to the LFG-carrying pipe.

Some embodiments, when designed primarily for this vertical mountingscheme, may be adapted using one or more fittings and lengths of hose toallow the device to mate with unions present on the existing system—inparticular, those found on wellheads.

Some embodiments may be designed to work best when installed at a slightangle in relation to the gas stream. For instance, if an eccentricorifice plate is used, the optimal installation may be one that anglesthe flow direction so that condensate preferentially streams along thewall nearest the orifice bore and away from the pressure or samplingports.

In some embodiments, the mounting feature on the device enclosure mayfeature a “T” configuration as in the figure below. Such a configurationmay allow the installation of the device on a riser pipe that comes outof the ground at an angle, while preserving a desired orientation withrespect to gravity or another reference.

In some embodiments, the ends of the pipe carrying the LFG stream thatruns through the enclosure may be tapered to provide for easierinsertion into mating connections on the system vacuum or extractionpoint connections, easing system installation.

In some embodiments, mounting features on the enclosure may be designedin such a way to also function as a handle or handles used when carryingand installing at the site, easing the deployment process.

Some embodiments may feature a handle or handles independent of mountingfeatures used to carry and install at a site, easing the deploymentprocess.

Designs and Methods for Field Serviceability

In some embodiments, the enclosure may be designed with a front panel294 allowing for service of one or more components.

In some embodiments, the orifice plate, orifice plate lid, and orificeslot may be designed to slide in through a slot accessible through thisfront panel.

In some embodiments, the gas sampling system may be arranged in such away to allow access to the calibration port 239 from this front panel.

In some embodiments, this front panel may contain a user interfaceconsisting of buttons and a text or graphic display that interfaces withthe internal electronics.

In some embodiments, this user interface can be used to toggle unitcommands including, but not limited to, initiating measurement cycles,initiating calibration cycles, changing valve command, opening aconnection to the server or initiating a purge command (for purging allfluid paths with clean air before the unit is uninstalled and removedfrom the LFG stream).

In some embodiments, the filtration system may employ a sensor 286 inline with the sample gas to measure characteristics after the filtersuch as, but not limited to, humidity or hydrogen sulfide content toprovide a gauge of filter health. For instance, as the adsorbent mediameant to filter hydrogen sulfide is consumed, the sensor after thefilter may register a higher concentration of hydrogen sulfide,eventually indicating that it is time to change the filter.

Some embodiments may incorporate one or more water detection or moisturesensors within the box to alert a technician of a failure in the filtersystem or presence of a leak.

Some embodiments may be assembled with a vapor corrosion inhibitor thatdeposits a corrosion inhibiting layer on exposed components within theenclosure.

In some embodiments, the gas sensor chamber may be assembled with avapor corrosion inhibitor that deposits a corrosion inhibiting layer onthe gas sensors.

Some embodiments may be assembled with desiccant to absorb any watervapor in the box introduced during assembly or maintenance access,preventing condensation on interior surfaces or electronics.

FIG. 19 illustrates a flowchart of an exemplary process 1000 of using aunit, such as unit 200, in some embodiments. The process 1000 begins atstage 1010. At stage 1010, gas may be flowed through a samplingsubsystem from a well riser pipe to a collection system, such ascollection system 110 shown in FIG. 1 . This flow may be achieved in anysuitable way, including by opening a valve that enables gas to flow fromthe landfill or by active control of a vacuum, as is known in the art.

The process 1000 may optionally proceed to stage 1020. At stage 1020, asample of the flowing gas may be passed into a sampling subsystem, suchas by controlling valves or otherwise enabling gas to flow into a unit200.

The process 1000 may optionally proceed to stage 1030. At stage 1030,moisture may be extracted from the sample of the flowing gas using athermoelectric condenser, such as the thermoelectric condenser 234.

The process 1000 may optionally proceed to stage 1040. At stage 1040, atleast one fluid is drained from the sample of the flowing gas using atleast one fluid knock-out, such as the at least one fluid knock-out 232.

The process 1000 may then proceed to stage 1050. At stage 1050, aportion of the sampling subsystem may be heated with the gas flowingfrom the well riser pipe to the collection system. The process 1000 maythen end for a given sample. The process 1000 may be continued orrepeated any number of times for other samples or for periodic or evencontinuous monitoring.

One or more aspects of the present application may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.For example, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments.

Also, the application may be embodied as a method, of which an examplehas been provided. The acts performed as part of the method may beordered in any suitable way. Accordingly, embodiments may be constructedin which acts are performed in an order different than illustrated,which may include performing some acts simultaneously, even though shownas sequential acts in illustrative embodiments.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

What is claimed is:
 1. An apparatus for sampling landfill gas extractedfrom a landfill and flowing through a pipe comprising a section havingat least one gas sampling port, the apparatus comprising: a sensorchamber; at least one sensor device disposed in the sensor chamber; agas flow passage between the at least one gas sampling port and the atleast one sensor device, wherein landfill gas extracted from thelandfill is configured to flow from the section of the pipe to the atleast one sensor device via the gas flow passage; at least one fluidknock-out disposed in the gas flow passage and configured to separate atleast one fluid from the landfill gas extracted from the landfillflowing from the at least one gas sampling port to the at least onesensor device; and at least one controller configured to reverse adirection of flow through the at least one fluid knock-out of the atleast one fluid separated from the landfill gas extracted from thelandfill.
 2. The apparatus of claim 1, further comprising an enclosureconfigured for coupling to the section of the pipe, and wherein the atleast one controller is configured to control an active heating elementto emit heat within the enclosure based at least in part on atemperature of the landfill gas extracted from the landfill.
 3. Theapparatus of claim 1, further comprising an enclosure configured forcoupling to the section of the pipe, and wherein the at least onecontroller is configured to control an active heating element to emitheat within the enclosure based at least in part on a temperature insidethe enclosure.
 4. The apparatus of claim 1, further comprising at leastone humidity sensor, disposed in the gas flow passage, for measuring ahumidity of the landfill gas extracted from the landfill.
 5. Theapparatus of claim 1, further comprising: at least one second sensordisposed in the gas flow passage between a filter and the at least onesensor device, and wherein the at least one controller is configured todetermine an efficacy of the filter based on one or more measurementsmade by the at least one second sensor.
 6. The apparatus of claim 5,wherein the at least one controller is configured to generate an alertbased on the determined efficacy of the filter.
 7. The apparatus ofclaim 1, wherein the at least one controller is configured to determinea measure of a flow rate of the landfill gas extracted from the landfillbased on a difference between a measure of pressure in the section ofthe pipe upstream of a constriction in the section of the pipe and ameasure of pressure in the section of the pipe downstream of theconstriction.
 8. The apparatus of claim 1, wherein the at least one gassampling port is rigidly coupled to the section of the pipe.
 9. Theapparatus of claim 1, wherein the at least one controller is configuredto control the at least one sensor device and wherein the at least onecontroller is located remotely from the at least one sensor device. 10.The apparatus of claim 1, further comprising an enclosure configured toreceive the section of the pipe.
 11. The apparatus of claim 1, whereinthe apparatus further comprises an enclosure for coupling to the sectionof the pipe and the enclosure comprises a panel such that the at leastone fluid knock-out can be accessed through the panel.
 12. The apparatusof claim 1, wherein the at least one fluid knock-out comprises a vesselhaving a first cross-sectional area larger than a second cross-sectionalarea of an inlet port to the at least one fluid knock-out and/or a thirdcross-sectional area of an outlet port to the at least one fluidknock-out.
 13. The apparatus of claim of claim 12, wherein the firstcross-sectional area is larger than the second cross-sectional area ofthe inlet port to the at least one fluid knock-out.
 14. The apparatus ofclaim 1, further comprising an orifice block comprising an inlet port tothe gas flow passage and an outlet port from the gas flow passage. 15.The apparatus of claim 14, wherein the at least one fluid knock-out isintegrated into the orifice block.
 16. The apparatus of claim 1, whereinthe at least one fluid comprises condensate.
 17. The apparatus of claim1, further comprising at least one valve disposed in the gas flowpassage between the at least one gas sampling port and the at least onefluid knock-out.
 18. The apparatus of claim 17, further comprising acalibration port configured for connection to at least one source of gasof known composition; and wherein the at least one valve is connectedbetween the calibration port and the at least one sensor device so as toenable gas to flow from the calibration port to the at least one sensordevice while isolating the at least one sensor device from the at leastone gas sampling port.
 19. The apparatus of claim 17, wherein the gasflow passage comprises a length of flexible tubing.
 20. A methodperformed by an apparatus for sampling landfill gas extracted from alandfill and flowing through a pipe comprising a section having at leastone gas sampling port, the apparatus comprising a sensor chamber; atleast one sensor device disposed in the sensor chamber, a gas flowpassage between the at least one gas sampling port and the at least onesensor device, at least one fluid knock-out disposed in the gas flowpassage, and at least one controller, the method comprising: flowinglandfill gas extracted from the landfill from the section of the pipe tothe at least one sensor device via the gas flow passage; separating,with the at least one fluid knock-out, at least one fluid from thelandfill gas extracted from the landfill flowing from the at least onegas sampling port to the at least one sensor device; and reversing, withthe at least one controller, a direction of flow through the at leastone fluid knock-out of the at least one fluid separated from thelandfill gas extracted from the landfill.
 21. The method of claim 20,wherein the apparatus further comprises an enclosure configured forcoupling to the section of the pipe and the method further comprisescontrolling, with the at least one controller, an active heating elementdisposed in the enclosure to emit heat within the enclosure based atleast in part on a measured temperature, wherein the measuredtemperature comprises a measured temperature of the landfill gasextracted from the landfill and/or a measured temperature inside theenclosure.
 22. The method of claim 20, further comprising obtaining ameasure of humidity of the landfill gas extracted from the landfill withat least one humidity sensor.
 23. The method of claim 20, furthercomprising determining a flow rate of the landfill gas extracted fromthe landfill based on a difference between a measure of pressure in thesection of the pipe upstream of a constriction in the section of thepipe and a measure of pressure in the section of the pipe downstream ofthe constriction.
 24. The method of claim 20, wherein the apparatusfurther comprises an enclosure for coupling to the section of the pipeand the enclosure comprises a panel such that the at least one fluidknock-out can be accessed through the panel.
 25. The method of claim 20,wherein the at least one fluid knock-out comprises a vessel having afirst cross-sectional area larger than a second cross-sectional area ofan inlet port to the at least one fluid knock-out and/or a thirdcross-sectional area of an outlet port from the at least one fluidknock-out.
 26. The method of claim 25, wherein the first cross-sectionalarea of the vessel is larger than the second cross-sectional area of theinlet port to the at least one fluid knock-out.
 27. The method of claim20, wherein the at least one fluid comprises condensate.
 28. The methodof claim 20, further comprising isolating the at least one sensor devicefrom the at least one gas sampling port by actuating at least one valvedisposed in the gas flow passage between the gas sampling port and theat least one fluid knock-out and coupled to the at least one sensordevice, the at least one gas sampling port, and a calibration portconfigured for connection to at least one source of gas of knowncomposition.